Assessment of the Structural Geological, Hydrogeological, and Geomorphological Relationships of the Athwelthota Landslide, Sri Lanka

Abstract

Landslides pose a significant threat to Sri Lanka, causing loss of life and property damages. The Athwelthota landslide in Kalutara District, occurred on May 26, 2017, resulting in casualties and severe property destruction. This study focuses on understanding the relationship between structural geology, hydrogeology, and geomorphology in the Athwelthota landslide area to comprehend the causes of landslides. We conducted field surveys, geotechnical investigations, and seismic surveys to gather data on geological features, soil properties, and rainfall patterns. The findings reveal that slope instability is influenced by the shear strength of soil overburden, jointed bedrock, deformation, and highly weathered garnet biotite gneiss. Groundwater flow through geological discontinuities and intense rainfall during the Southwest Monsoon contribute to increased pore water pressure and reduced shear strength, triggering landslides. The study emphasizes the importance of assessing these factors for hazard assessment, early warning systems, and sustainable development in landslide-prone regions. By understanding the geological and hydrological characteristics of the area, it is possible to identify vulnerable areas and implement appropriate mitigation measures. This research is part of a larger project aimed at developing an early warning technology for rain-induced rapid and long-traveling landslides. The insights gained from this study can help land-use planning, infrastructure development, and disaster management strategies in landslide-prone areas, ultimately contributing to the protection of lives, reduction of property damage, and the sustainable development of the region.